Category: ASP.NET

22 Mar 2017 12:52

Joined:	10/11/2007
Level:	Silver
Points:	155

Points:	5

Why not getting Request.QueryString value in asp.net

Hi,
I am passing value to another form from dropdowlist and textbox.
But I not getting Request.QueryString value in another aspx page.
So it is showing error..
'Object reference not set to an instance of an object.'

First form code:
----------------
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
GM.SetProjectData(this.ddlProjectName, 0);

this.ddlProjectName.Items.Insert(1, new ListItem("All", "-1"));

this.GetProjectTollData();

this.tbStartDate.Attributes.Add("readOnly", "readOnly");

string _URL = "javascript:window.open('NewDefaultTollResult.aspx?ProjectName=" + this.ddlProjectName.SelectedIndex + "TollID=0" + "TollDate=" + this.tbStartDate.Text.ToString() + "');";

bFind.Attributes.Add("onclick", _URL);
}
}

protected void bFind_Click(object sender, EventArgs e)
{
TollEntity tollEntity;
TollLogic tollLogic;

try
{
tollEntity = new TollEntity();
tollLogic = new TollLogic();

if (GM.ConvertToDate(this.tbStartDate.Text) == GM.ConvertToDate(DateTime.Now.ToString("dd-MM-yyyy")))
{
ScriptManager.RegisterStartupScript(this, this.GetType(), "Msg", "alert('Invalid Date, You cannot check today Date..');", true);
return;
}

if (this.ddlProjectName.SelectedIndex > 0 && this.ddlTollName.Items.Count == 0 && this.tbStartDate.Text.Trim() != string.Empty)
{

ScriptManager.RegisterStartupScript(Page, typeof(Page), "OpenWindow", "window.open('NewDefaultTollResult.aspx?ProjectName=" + this.ddlProjectName.SelectedValue + "TollID= 0" + "TollDate=" + this.tbStartDate.Text.ToString() + "');", true);
}
else if (this.ddlProjectName.SelectedIndex > 0 && this.ddlTollName.SelectedIndex > 0 && this.tbStartDate.Text.Trim() != string.Empty)
{

ScriptManager.RegisterStartupScript(Page, typeof(Page), "OpenWindow", "window.open('NewDefaultTollResult.aspx?ProjectName=" + this.ddlProjectName.SelectedIndex + "TollID=" + this.ddlTollName.SelectedValue + "TollDate=" + this.tbStartDate.Text.ToString() + "');", true);
}

//this.GetProjectTollData();
}
catch (Exception ex)
{
throw ex;
}
finally
{
tollEntity = null;
tollLogic = null;
source = null;
}
}

Second form code:
----------------
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
if (Request.QueryString["ProjectName"].ToString() != string.Empty && Request.QueryString["TollID"].ToString() != string.Empty && Request.QueryString["TollDate"].ToString() != string.Empty)
{
this.SetProjectTollData();
}
}
}

#769077

22 Mar 2017 19:34

Joined:	18/12/2008
Level:	Gold
Points:	2921

Points:	4

Hi,

This error is caused because you are trying to access a property of an object that is null.

Whenever you get this sort of error, you can try to step through and debug your source code.
This will help you get to the line that is throwing the error.

You can take a look at which object is null and then fix this error by figuring out why this object is null in your code.

To understand is that really null, Check like following


string _URL = "javascript:window.open('NewDefaultTollResult.aspx?ProjectName=" + TestProj + "TollID=0" + "TollDate=" + this.tbStartDate.Text.ToString() + "');";

hardcode some value in the Project Name parameter and check it out you are getting the projname in the next function.

Thanks,
Mani

#769093

24 Mar 2017 09:10

Joined:	03/05/2013
Level:	Gold
Points:	15822

Points:	3

Hi,

As per error 'Object reference not set to an instance of an object.' whenever you try to assign null value to some object that time you may get this type of error.

My suggestion to assign any value before that you have to check whether it is null or not null. if not null then assign value otherwise skip for assign.

Ex:


if(value!=null)
{
       int i=value;
}

Hope this helps you...

--------------------------------------------------------------------------------
Give respect to your work, Instead of trying to impress your boss.

N@veen
Blog : http://naveens-dotnet.blogspot.in/

#769102

24 Mar 2017 17:04

Joined:	13/06/2007
Level:	Gold
Points:	21327

Points:	3

''Object reference ' error indicates you are trying to access NULL value, when your query string is NULL at that time application is throwing the exception.
before accessing value from 'Request.QueryString' check if it is NULL


if(Request.QueryString["val1"] != null)
   {
        //your code goes here
   }
   else
  {
         //query string is NULL
 }

Thanks
Koolprasd2003
Editor, DotNetSpider MVM
Microsoft MVP 2014 [ASP.NET/IIS]

#769123

30 Mar 2017 09:03

Joined:	30/04/2012
Level:	Gold
Points:	7233

Points:	2

You can try this code example in C# to getting Request.QueryString value in asp.net

 string fullname1 = Request.QueryString["fullname"];
string fullname2 = Request["fullname"];/code]

#769766
18 Sep 2018 11:33

Joined: 28/09/2005
Level: Gold
Points: 637
Points: 4

Joined:	28/09/2005
Level:	Gold
Points:	637

'Object reference ' error generally throws when you are trying to get the query param value without checking of null condition, when your query param not passed then , default it is null and when you assign this it will throw exception.

So, if you can write code as like below then you won't get null exception and always it will give you some value if you pass query param otherwise it will assign "" but not throw object reference exception.

string fullname1 = Request.QueryString["fullname"] + "";
string fullname2 = Request["fullname"] + "";

Hope this will resolve your problem
Thanks!
B.Ramana Reddy

#769773
23 Sep 2018 16:40

Joined: 08/09/2004
Level: Gold
Points: 854
Points: 3

Joined:	08/09/2004
Level:	Gold
Points:	854

Unit unless the value it exists in the first place, You will not be able to get the value using Request.QueryString . It will be great if you can debug and check the quesrystring param values before redirect.  If Is that something you are creating on the page and want to preserve on postback? In that case, use ViewState to store the value and use across postbacks.
Debasmit Samal

#769819
27 Dec 2018 12:25

Joined: 29/06/2010
Level: Silver
Points: 267
Points: 4

Joined:	29/06/2010
Level:	Silver
Points:	267

Hello,

In the first form code you haven't provided the "&" symbol for the multiple values.That's why this kind error arising.Replace your this part of coding (first form code) with the modified one which is mentioned bellow:-

Your Code
---------
string _URL = "javascript:window.open('NewDefaultTollResult.aspx?ProjectName=" + this.ddlProjectName.SelectedIndex + "TollID=0" + "TollDate=" + this.tbStartDate.Text.ToString() + "');";

Modified Code
-------------
string _URL = "javascript:window.open('NewDefaultTollResult.aspx?ProjectName=" + this.ddlProjectName.SelectedIndex + "&TollID=0" + "&TollDate=" + this.tbStartDate.Text.ToString() + "');";

Thanks

Why not getting Request.QueryString value in asp.net

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